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Arapahoe County's Urban Evolution on Iliff Avenue


Iliff Avenue is a major east-west urban throughfare running across the Denver metropolitan area. As a significant commuter route serving residential, commercial, and industrial users, this tightly packed multi-modal corridor was faced with safety concerns and aging infrastructure, including a deteriorating bridge, joint failure, pavement decay, and potholes.




Collaborating with Atkins, Ground Engineering, and Geocal, SEH was selected by Arapahoe County to provide construction administration and oversight for the reconstruction of Iliff Avenue, including two structure widenings and over two miles of urban arterial between Parker Road and Quebec Street. The project involved careful coordination with key stakeholders, including the City and County of Denver and the Colorado Department of Transportation (CDOT.) From underground storm sewer systems, electrical utilities, gas utilities, all the way up to signals and lighting infrastructure, the entire corridor received a complete upgrade.

Widening the Cherry Creek Bridge

One of the unique aspects of this project was the need to widen both sides of the Cherry Creek Bridge to accommodate the expanded roadway. This involved collaboration with the US Army Corps of Engineers for their annual flow releases from Cherry Creek Reservoir. During the releases, water levels rise two or three feet above the current bike and pedestrian path located below the bridge, making meticulous coordination crucial to smoothly integrate the bridge modifications with the overall reconstruction efforts.

Mitigating Asphalt Joint Failure with Hot Lapping

To address the challenge of pavement joint failure, the construction team implemented a technique known as hot lapping. In this approach, asphalt pavers completed a second pass before the pavements were fully compacted. The result was a pavement with nearly invisible joints, significantly reducing the risk of joint failure. By improving the joint quality, years have been added to the life of the pavement. This not only ensures a safer and more reliable transportation system but also translates into tangible cost savings for the county and its taxpayers, as maintenance and upkeep will be minimal.

Project Phasing and Successful Impact

Considerable phasing was performed to keep access open for the traveling public as the project took place over 11 intersections. To avoid subgrade issues during the phasing, special subgrade was used to bear the loads transmitted and ensure a stable, long-lasting roadway. 

The positive feedback from communities, including nearby shopping centers and redevelopment projects, underscores the project's impact, promising a sustainable urban landscape for Arapahoe County for years to come.


Iliff Avenue Corridor Reconstruction 


Arapahoe County, Colorado


Arapahoe County

  • Over two-mile urban arterial with two structure widenings, including the Highline Canal Structure
  • Cement-treated subgrade (CTS) adhesion to asphalt paving
  • Mechanically stabilized earth (MSE) walls, fencing, and drainage
  • Implementing cofferdams to support bridge falsework
  • Extension of the Highline Canal, an irrigation canal structure and accompanying trail system
  • Construction administration
  • Value engineering